HSPA5 and rheumatoid arthritis: For example, in rheumatoid arthritis BiP at the cell surface can stimulate tumor necrosis factor (TNF) production to promote inflammation, but BiP can also act as an antigen to stimulate CD8-positive T cells leading to increased production of the anti-inflammatory cytokine IL-10 (Bodman-Smith et al., 2003; Lu et al., 2010).